“My average that comes in on time is seven students out of 30,” Ms. Covington told me recently as she surveyed a bank of empty laboratory tables in her first-period living environment class. Of the truant students, she lamented: “They stroll in. And then I have no-shows.”

Now Wadleigh is trying a new approach to absenteeism. In November, the school began using Kinvolved, an app that lets teachers take each student’s attendance with the swipe of a finger, and then automatically sends a text message to parents if a child is absent or tardy. Teachers can customize lateness alerts to include the number of class minutes missed. (The school does not copy students on these messages.)

Ms. Covington said she could already see a deterrent effect. “This one, you used to hardly ever see,” she said, indicating a ninth grader perched behind a lab table, pencil and notebook at the ready. “Now she is one of the first in class in the morning.”

For parents who may feel irked by receiving up to nine truancy or tardiness messages in a day, however, the app may take some getting used to.

“There was one parent who said, ‘Please stop sending me these messages,’” said Habib Bangura, the community school director for Wadleigh’s partnership with Teachers College, Columbia University, which is an effort to improve educational outcomes in high-need Harlem schools. “They asked to be removed, just like a telemarketer. We were happy to oblige.”

Kinvolved is one of many apps and software services aimed at automating or streamlining longstanding school practices, like classroom behavior management or exam proctoring. Kinvolved Inc., the three-year-old start-up that developed the app, was founded by two entrepreneurs in their 20s, Miriam Altman and Alexandra Meis, who met as graduate students at the Robert F. Wagner Graduate School of Public Service at New York University.

Ms. Altman, Kinvolved’s chief executive, previously taught history at a high school in Manhattan. As is the case in many districts, she was required to take attendance by hand using bubble sheets, marking her students “A” for absent or “L” for late.

The sheets were fed into a processor, with each “A” leading to a robocall to warn parents. But the system that sent automated voice mail messages often had out-of-date family contact information.

Kinvolved’s goal is to spur greater parental involvement by increasing the details parents receive from their child’s school while making the communication process more efficient. In addition to sending attendance notices in English, Spanish, Haitian Creole and other languages, teachers may use the app to inform parents about school events or class tests.

For administrators and teachers, the app also includes pie charts showing schoolwide or student-specific attendance trends, such as lost instructional time in a given week or month. The Teachers College partnership program is covering the cost of Kinvolved, which can run $2,600 to $10,000 per school year, for five Harlem schools.

Daisy Fontanez, the principal of Wadleigh, likens the school’s adoption of Kinvolved to “accountants who used to enter financial information by hand — and then the Excel spreadsheet came out.”

Parents may also see Kinvolved as a counterweight to the increased autonomy mobile phones can confer upon children.

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Kinvolved in action. The app helps teachers take attendance and automatically sends a text message to parents if a student is absent or tardy.

“There’s a lot of new technology, like cellphones, that have undercut parent influence in socializing their children and increased peer influence,” says Patricia Greenfield, a psychology professor at the University of California, Los Angeles. “This restores a bit of parents’ ability to socialize their children in a very constructive way.”

Like a number of school apps that slice off symptoms of complex problems and tackle them as information deficiencies, however, Kinvolved also raises questions about technologies that treat students more as subjects to be surveilled and analyzed than as participants in their own education.

“I get why these interventions are sexy — because they are relatively cheap,” says Kevin Gee, an assistant professor of education at the University of California, Davis, where he studies the effectiveness of educational policies.

But text-based programs, such as school letters that inform parents that their children are overweight, he said, often rely on a hypothesis that more information naturally results in better outcomes for students. Professor Gee added, “Is information enough to move the needle on this problem?”

Ms. Altman said that Kinvolved’s staff members coached school administrators to help them use attendance data to shape the programs they put in place.

“We believe that technology alone is not going to solve any problem,” she said.

At Wadleigh, administrators tend to view Kinvolved as a detection system for habitual absenteeism — not as a means to address underlying problems, like family illnesses, job loss or homelessness, which may cause students to miss school.

“Kinvolved is a tool that gives us the attendance number, but it doesn’t give us the qualitative information that will allow us to address the issue,” said Mr. Bangura, Wadleigh’s community school director. “There are legitimate and structural reasons that some students are late to school” — like the responsibility to drop off younger siblings at a babysitter — “and we are trying to put some solutions in place by communicating with the family.”

The school has used data logged by Kinvolved to direct additional attention to those families whose children miss school most often. The students meet regularly with advisers and mentors to set monthly attendance improvement goals. The school rewards students who meet their monthly goals, giving them a free movie ticket.

Teachers at Wadleigh have also taken it upon themselves to share Kinvolved data with their students. “I like them to see how many minutes late they are,” said Jillian Fisher, a social studies teacher. “It takes the guesswork and the excuses out of it.”

Administrators also invite parents to meetings so they can join forces to improve a student’s attendance.

One morning this month, a couple arrived at school after having received text messages saying their daughter had been late to school and was also skipping classes after lunch. They huddled with Mr. Bangura to discuss strategies for motivating their daughter to go to class.

“She says she is coming in to school,” her father said. “But the picture is not so pretty as she paints.”

It seems clear that school attendance efforts will not succeed without devoted teachers like Ms. Covington who, even without an app, have developed their own internal radar that tracks truant students who may be at risk of falling behind.

As Ms. Covington walked down a school hallway lined on either side with yellow student lockers, she caught sight of a ninth grader ducking into a classroom. The teacher deftly caught the student, who had missed her first-period science class that day, by the elbow.

“When are you coming to me to make up class?” Ms. Covington asked.

In education, the killer app is the teacher.

A version of this article appears in print on , on Page BU3 of the New York edition with the headline: Looking Beyond a Classroom’s Empty Seats. Order Reprints | Today’s Paper | Subscribe